Publications
Publication Information
| Title | A High Precision Measurement of the Proton Charge Radius at JLab |
| Authors | Weizhi Xiong |
| JLAB number | JLAB-PHY-20-3266 |
| LANL number | (None) |
| Other number | DOE/OR/23177-5059 |
| Document Type(s) | (Thesis) |
| Associated with EIC: | No |
| Supported by Jefferson Lab LDRD Funding: | No |
| Funding Source: | Nuclear Physics (NP) |
|
Thesis A PHD thesis Advisor(s) : Haiyan Gao (Duke) | |
| Publication Abstract: | The elastic electron-proton (e-p) scattering and the spectroscopy of hydrogen atoms are the two traditional methods to determine the proton charge radius (r_p). In 2010, a new method using muonic hydrogen (µH)^1 spectroscopy reported a rp result that was nearly ten times more precise but significantly smaller than the values from the compilation of all previous r_p measurements. This discrepancy is often referred to as the ?proton charge radius puzzle?. In order to investigate the puzzle, the PRad experiment (E12-11-106^2) was first proposed in 2011 and performed in 2016 in Hall B at the Thomas Jefferson National Accelerator Facility, with both 1.1 and 2.2 GeV electron beams. The experiment measured the e-p elastic scattering cross sections in an unprecedented low values of momentum transfer squared region (Q^2 = 2.1× 10^-4-0.06 (GeV/c)^2), with a sub-percent precision. The PRad experiment utilized a calorimetric method that was magnetic-spectrometer-free. Its detector setup included a large acceptance and high resolution calorimeter (HyCal), and two large-area, high spatial-resolution Gas Electron Multiplier (GEM) detectors. To have a better control over the systematic uncertainties, the absolute e-p elastic scattering cross section was normalized to that of the well-known Møller scattering process, which was measured simultaneously during the experiment. For each beam energy, all data with different Q^2 were collected simultaneously with the same detector setup, therefore sharing the same integrated luminosity. The windowless H2 gas-flow target utilized in the experiment largely removed a typical background source, the target cell windows. The proton charge radius was determined as r_p = 0.831±0.007_stat.±0.012_syst. fm, which is smaller than the average r_p from previous e-p elastic scattering experiments, but in agreement with the µH spectroscopic results within the experimental uncertainties. |
| Experiment Numbers: | E12-11-106 |
| Group: | Hall A |
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